Selenium is an essential trace mineral that is important for many bodily processes, including cognitive function, a healthy immune system, and fertility in both men and women. Selenium is a constituent of more than two dozen selenoproteins that play critical roles in reproduction, thyroid hormone metabolism, DNA synthesis, and protection from oxidative damage and infection
It contributes to thyroid hormone metabolism and DNA synthesis, and it helps protect against oxidative damage and infection, according to the United States Office of Dietary Supplements.It is present in human tissue, mostly in skeletal muscle.
Dietary sources are varied. They include Brazil nuts, seafood, and meats.
The amount of selenium in food often depends on the selenium concentration of the soil and water where farmers grew or raised the food.